CA1242100A

CA1242100A - Photosensitive transfer material and process for manufacturing a photoresist stencil

Info

Publication number: CA1242100A
Application number: CA000437782A
Authority: CA
Inventors: Ulrich Geissler; Walter Herwig; Helga Sikora
Original assignee: Hoechst AG
Current assignee: Hoechst AG
Priority date: 1982-10-02
Filing date: 1983-09-28
Publication date: 1988-09-20
Also published as: ES8501539A1; EP0105421A1; IL69876A; EP0105421B1; FI74156B; IL69876A0; AU1986283A; JPS5975245A; JPH0612413B2; KR840006419A; ES526181A0; DE3236560A1; FI833517A0; US4559292A; FI74156C; DE3377022D1; KR910004874B1; FI833517A; ATE35060T1; AU558773B2

Abstract

Abstract of the Disclosure The present invention relates to a photosensitive transfer material, which comprises a flexible temporary support film which is preferably transparent, a thermo-plastic photosensitive layer, optionally a flexible cover film on the free side of the photosensitive layer and, optionally, an intermediate layer between the support film and the photosensitive layer. The photosensitive transfer material is suitable for manufacturing photore-sist stencils and solder masks. The temporary support film has a rough surface which exerts an embossing effect on the surface of the photosensitive layer and the inter-mediate layer, respectively. The mat-finish of the intermediate layer prevents an irregular deformation of this layer in moist air, while the mat-finish of the photosensitive layer precludes unwanted reflections.

Description

Hoe 82/K 054 PHOTOSENSITIVE TRANSFER MATERIAL AND PROCESS
OR MANUFACTURING A PHOTORESIST STENC _ The present invention relates to a photosensitive transfer material comprising a temporary flexible support film and a thermoplas-tic photosensitive layer. The inven-tion further relates to a process for manufacturing a photoresist stencil, in which a solid thermoplastic photosensi-tive layer is transferred to a permanent suppor-t by means of a transfer material and is exposed imagewise and developed on this permanent support.
Transfer processes and transfer materials of the above-mentioned -type are, for example, described in German Patent No. 1,522,515 or in U. S. Pa-tent No. ~,193,797.
According to these patents, negative-working or positive-working thermoplastic photosensitive layers are transfer-red in the dry state, under pressureor with heating, to a permanent support and are processed into a photoresist stencil. The permanent support is -then modified, for example etched or electroplated, in the areas not covered by -the stencil.
In Bri-tish Patent No 1,323,792, and in I. S. Pa-tent No. 3,88~,693, corresponding materials are described, in which a non-thermoplastic intermediate layer is applied between the photosensitive layer and the temporary support.
This non-thermoplastic intermediate layer is capable of being dissolved in -the developer used for processing the photosensiti.ve layer and it has a greater adherence to the photosensiti.ve layer -than to the temporary support. These materials are processed by laminating the photosensitive layer to the permanent support and then stripping the Hoe 82/K 05~

temporary support from the intermediate layer. Only after these operations is the material contact-exposed under a master and then developed. Because the preferred inter-mediate layers are water-soluble, they tend to swell in the air, depending on the atmospheric humidity, and form surfaces having an irregular texture, which considerably complicates or even prevents correct exposure.
U. S. Patent No. 4,278,752 discloses the production of solder masks according to the dry resist process. It has been found -that, in this application, and also in the afore-mentioned use, the high-gloss surface of the resist layer remaining after stripping the temporary support film, is inconvenient in some cases. Under particular soldering conditions, it can also occur that threads or pellets of the solder alloy adhere to the surface of the solder mask after wave-soldering, which may possibly lead to short circuits. In addition, the glossy surface gives rise to dlsturbing reflections, particularly when components are manually inserted.
In -the case of a dry resist, a mat resist surface with its markedly reduced reflections, compared with the copper surface, makes it possible to inspect a developed printed circuit board by optical means.
U. S. Patent No. 3,891,443 describes photopolymer-izable relief printing plates, in which the surface of the photopolymerizable layer is matted, in order to im-prove and accelerate contact between the master and the photopol~merizable layer in the vacuum printing frame and to improve ink receptivity in flexographic printing. Mat-finishing of the surface may, for example, be effected by I% Hoe 82/K 05~

contacting the surface wl-th a matted or grained surface, for example with a roughened aluminum sheet or a roughened polyester film. In the process, the mat-finish surface is coated with a silicone in order to enable -the subsequently necessary removal from the layer. Processing of a photo-sensitive printing plate differs widely Erom that of a dry resist material and -the object which is, in the former case, achieved by ma-t-finishing the surface of the photo-sensitive layer, is different from the problem involved, as described above, in the processing of dry resists into solder masks or resist stencils.
It is an object of the present invention to provide a transfer material which does not give rise to problems upon exposure, if in-termediate layers which are water-soluble or swellable in moist air are used and which does not show a high-gloss layer surface, after stripping the temporary support film.
The present invention provides a photosensitive transfer material of the above-described kind.
In the material accordiny -to the present invention, the suppor-t film has a rough surface facing the photosen-sitive layer.
According to the present invention, a process for manufacturing a photoresist stencil is Eurther provided, in which a thermoplas-tic photosensitive layer, which is applied to a flexible support film, is laminated wi-th the free surface thereof to a permanent support, and the photosensitive layer is then exposed imagewise and is devel-oped into a relief image, af-ter stripping the flexible support film.

Hoe 82/K 054 In the process of the invention, a transparent sup-port film is used, in which the surface carrying the photo-sensitive layer is rough and the photosensitive layer is exposed through the support film, before the latter is stripped.
According to a further embodiment of the process of this invention, a transfer ma-terial comprising a temporary support film, a thin intermediate layer which does not become lacy upon heating to temperatures up to about 150 C, and a thermoplastic photosensitive layer applied on top of the intermediate layer, the intermediate layer adhering more firmly to the photosensitive layer than to the support film and being soluble in a developing liquid used for the photosensitive layer, is laminated to a permanent support with the free surface of the pho-tosensitive layer, the temporary support film is stripped and the photosensitive layer is exposed imagewise and developed into a relief image.
In the process of the invention a temporary suppor-t film is used, which has a rough surface, on which the intermedia-te layer and the photosensitive layer are present.
Preferably, the surface of the transfer material of the present invention, which faces away from the temporary support film, carries a cover film wi-th less adherence to the photosensitive layer than the support film.
The rough surface of the temporary support film can be produced by mechanical roughening, for example by sandblasting, or by embedding minute particles. A pre-ferred film comprises in its mass uniformly distributed particles, for example, of silicon dioxide, talcum,

2~
Hoe 82/K 054 magnesium oxide, boron ni-tride, aluminum oxide or high-melting insoluble organic substances The amount of particles preferably ranges from about 0.5 to 6 percent by weiyht, based upon the weight of the film.
The roughness of the support film should, in general, be in -the range from 0.3 to 10 em, preferably from 0.5 to 5 em. Roughnesses in the upper region of the ranges given are employed for -thicker photosensitive layers and those in -the lower region for thin layers, in particular, if the relatively thin intermediate layers are present.
If the roughness of the film surface is produced by embedding particles in the film, the particle size is, on an average, slightly grea-ter than the desired roughness;
particle size may, for example, amount to 1.5 -to 2.5 times the desired roughness.
The temporary support film should be transparent in those cases in which an intermediate layer is no-t used.
It is then necessary -to select the amount and -the index of refrac-tion of the embedded par-ticles in such a way that transparency is not substantially affected. For -this pur-pose, a combination of polyethylene terephthala-te films with silicon dioxide particles has proved particularly favorable. Generally, the film may comprise the materials specified in U. S. Patent No. 3,884,693.
U. S. Patent No. 3,884,693 also men-tions materials which are suitable for the preparation of the intermediate layer. Advantageous subs-tances are, for example, poly-vinyl alcohol, polyvinylpyrrolidone and acrylamide poly-mers. The intermedia-te layer has a thickness ranging from about 0.05 -to 8 em, preferably from 1 -to 5 em.

Joe 82/X 054 It may be particularly advantageous to add a small amount of at least one constituent of the photosensitive layer to the intermediate layer. Such an addition will have a favorable effect on the adherence to the pho-tosen-sitive layer and the separation from the support film.
This embodiment has proved particularly useful, if the photosensitive layer comprises a photopolymerizable layer and if -the layer constituent added -to the intermediate layer is, in the first place, -the polymerizable compound.
The photosensitive layer may comprise a posi-tive-working or a negative-working layer, i.e. it is either solubilized or hardened by exposure. Usually, photopo-lymerizable layers are preferred, which are generally composed of a polymerizable compound, particularly a com-pound with at least two acrylic acid ester or methacrylic acid ester groups, a photoinitiator for the free-radical initiated chain polymerization, a polymeric binder, and other conventional additives. Layers of this kind and other negative-working layers are, for example, described in German Patent No. 1,522,515, U. S. Paten-ts Nos.

3,884,693 and 4,278,752, and in German Offenlegungsschrift No. 3,036,694.
Suitable positive-working layers are, in particular, those based on 1,2-quinone diazides or acid cleavable com-pounds. Layers of this kind are described in U. S. Patents Nos. 4,193,797; 4,101,323; and 4,247,611.
The free side of the photosensitive layer is prefer-ably covered with a cover film with less adherence to the pho-tosensitive layer than the temporary support film, for example, a film of polyethylene.

Hoe 82/K 05D~

The material according to the presen-t invention is processed in such a manner -that the optionally present cover film is removed and the uncovered or free surface of the thermoplastic photosensitive layer is, preferably under pressure and with heating, laminated to the perma-nen-t support, preferably a circuit board or a copper-clad base material, respectively. If there is no intermedia-te layer between -the temporary support film and the photo-sensitive layer, exposure is subsequently effec-ted through the support film, the support film is stripped and the exposed photosensitive layer is developed. In the case of a solder mask, development is followed by tempering. Due -to the mat appearance -thereof, the surface of the resist stencil is readily visually distinguished from the uncovered copper surface so that evaluation of -the copy is facilitated. In the subsequent soldering operation, -the mat surface of -the solder mask surprisingly remains free from threads or pellets formed from -the solder, for example, a lead-tin alloy.
If a conven-tional photoresist stencil is involved, development is followed by etching the uncovered base metal or depositing metal thereupon, usually in an elec-troplating process.
In the processing of a material which comprises an intermediate layer between the support film and the photo-sensitive layer, the support film is stripped af-ter the laminating process and the master is then placed upon the in-termedia-te layer which has been embossed by the rough surface of the support film. The intermedia-te layer which is textured or mat-ted as a result of the embossing effect Hoe 82/K 05~

does not show any tendency to irregular swelling or dis-tor tion phenomena, even when i-t is kept in moist air for a prolonger period, so that perfect contact printing is possible.
If the photosensitive layer comprises a pho-topolym-erizable mixture and is, therefore, sensitive to atmos-pheric oxygen, care must be taken that the intermedia-te layer applied is not thinner than the surface roughness of the support film. Otherwise, there is a risk -that this layer, which simultaneously serves as an oxygen barrier, is interrupted in places and there loses its protective function. Generally, it is still possible to obtain con-tinuous polyvinyl alcohol layers, if layer thicknesses are only slightly greater, approximately by a few tenths of a em, than the maximum roughness of the film.
The materials of the present invention are contact-exposed under transparent masters, using short wave vis-ible or ultraviolet light supplied by conventional printing lamps, as is known in the art. It is also possible to image the layers by means of laser irradiation. It is a particular advantage -that the invention also resul-ts in a reduction of the required quantity of light, i.e., in an increase of the effective photosensitivity.
The following examples describe preferred embodi-ments of the invention. Percentages and quantitative ratios are to be understood as denoting units of weigh-t, unless o-therwise indicated. Parts by weight (p.b.w.) are related to parts by volume (p.b.v.) as the g is related to the ml.

_ Hoe 82/K 05 Example 1 A coating solu-tion was prepared of 13 p.b.w. of a terpolymer formed from n-hexyl methacrylate, methacrylic acid and styrene (60:30:10), having an aver-age molecular weight of about 35,000 and an acid number of 195,

4.4 p.b.w. of polyethylene glycol-400-dimethac-rylate, 1.6 p.b.w. of an elastomeric reaction product of glycidyl methacrylate, adipic acid and an oligomeric diisocyanate obtain-ed by reacting tolylene diisocyanate with a polybutane-1,4-diol of Ger-man Offenlegungsschrift No. 3,036,~94), 1 p.b.w. of hexamethoxymethyl melamine, 0.2 p.b.w. oi 9-phenyl acridine, 0.01 p.b.w. of a blue azo dye obtained by coupling 2,4-dinitro-6-chlorobenzenediazonium sal-t with 2-methoxy-5-acetylamino-N,N-diethylaniline, and 0.03 p.b.w. of 1,4-bis-(4--tert. butoxy-phenyl-amino)-5,8-dihydroxyanthraquinone in 30 p.b.w. of butanone, and

5.0 p.b.w. of ethanol.
110 cm wide webs of 23 em thick polyethylene tere-phthalate films, one film being smoo-th and -the o-ther pigmented with porous silicon dioxide having an average par-ticle diameter of 1 em, were continuously coated wi-th this solution, by means of a slot die. after passing Hoe 82/K 05 through a drying zone, the resist layers had, in each case, a thickness of 100 em and were then covered with a 25 ~tm thick polypropylene film. A slitter was used to cut the dry resist films thus produced into handy resist rolls which had a width of ~5 cm and a web length of 50 m.
The laminating tests were carried out using test boards of an epoxy-fiberglass laminate, provided with approximately 65 em thick conductive paths of copper hav-ing a tin-plated surface and plated-through holes. The widths and distances of the conductive paths were in the range between 200 and 1000 em; the holes had diameters ranging from 0.6 to 4 mm.
The solder resist layers of 100 em thickness were laminated to these boards at 120 C, using a commerical lamina-tor.
In a commercial exposure apparatus with a 5 kW metal halide lamp, the boards were exposed for 25 seconds through a master covering -the pads and holes -to be soldered, then developed wi-th an 0.3 percent concentra-tion soda solution for 150 seconds in a commercial spray processor, and blown dry. The printed circuit boards prepared in this way were subsequently baked for 60 minutes at 150 C in a drying cabinet. After cooling down, the boards were we-tted with a Elux, TL 33-16 manufactured by Alpha Grillo, and then passed over a commercial lead-tin wave-soldering bath at 250 C, at a conveying speed of 1.0 m/mln.
The printed circui-t boards which had been coated wi-th -the above-described mat-~inish solder mask were absolutely clean after soldering and cleaning.
~r,dolP

~2~2~
Hoe 82/K 054 Under particular soldering conditions tfor example, if the film of flux had insufficiently dried), the solder resist layer which had been transferred from a smooth polyes-ter film developed defects caused by pellets or -threads of the solder which adhered to -the solder mask and could not be removed, even by a cleaning operation.
Such defec-ts will lead to short circuits and the printed circuit board is useless.
Obviously, lead-tin particles adhere less to a mat-finish, i.e. roughened resist surface, than to a glossy, i.e., planar, surface.
Example 2 Coating solutions were prepared as described in Example 1, in which the following monomers were substituted for polyethyleneglycol-400-dimethacrylate:
(a) reaction product of 2,2,4-trimethyl-hexamethyl-ene-diisocyanate and hydroxyethyl methacrylate, (b) reaction product of triethylene glycol, 2,2,4--trimethyl-hexamethylene-diisocyanate and hydroxyethyl methacryla-te, (c) 2,2-bis-[4-(2-acryloyloxy-propoxy)phenyl]-propane.
As indicated in Example 1, the solutions were coated upon a smooth polyester film, and a polyester film which had been pigmented with silica gel and polypropylene films were laminated to the layers after drying. The dry resist films were processed as descrlbed in Example 1.

In this example, it was again found that no lead-tin residue adheres to the mat surface ox the solder mask after soldering, whereas in the glossy surface adhering residue occurs under unfavorable conditions.

2.'L~D

Hoe 82/K 054 Example 3 A. The solution for preparing the pho-tosensitive layer had the following composition:

6. 5 p. b.w. of a terpolymer formed rom n-hexylmethacrylate, methacrylic acid and styrene (60: 30 :10), having an average molecular weight of about 35, 000 and an acid number of 195, 3.2 p.b.w. of polyethyleneglycol-400-dimethac-ryla-te, 0.8 p.b.w. of the elastomer mentioned in Example 1, 0.1 p.b.w. of 9-phenyl acridine, 0.035 p.b.w. of an azo dye, obtained by coupling 2,4-dinitro-6-chlorobenzenediazonium salt with 2-methoxy-5-acetylamino-N-cyanoethyl~N-hydroxyethyl-aniline, p.b.w. of methylethylketone, and l p.b.w. of ethanol.
B. The solution or preparing the intermediate layer had -the Eollowing composition:
200 p.b.w. of a 7 percen-t concen-tra-tion aqueous polyvinyl alcohol solution, 1 p.b.w. of polyethyleneglycol-~00-dimethac-rylate, and 0.002 p.b.w. of crystal violet.

C. A biaxially stretched and heat-set polyethylene terephthalate film which had a thickness of 25 em and had been provided with an about 1 em thick intermediate layer of polyvinyl alcohol, using solution B, was spin-coated ~2J~
Hoe 82/K 054 with coating solution A, in such a way that a layer weight of 40 g/m was obtained af-ter drying at 100 C.
D. Operation C was repeated, however, using a poly-ethylene terephthalate film which had a rough surface resulting from an addition of about 1.5% by weight of porous silicon dioxide having an average particle size of 1 em.
A commercial laminator was employed for laminating the dry resist films obtained according to C and D at 120 C to glass fiber reinforced epoxylarninates, clad with 17.5 ~.~m thick copper foils. After cooling to room temperature, the polyester films were stripped.
The surface conditions were observed and recorded as a function of time and atmospheric humidi-ty:

S-torage time in minu-tes 2 4 4 180180 relative in 30 80 30 80 30 80 _ .
mat mat mat mat mat mat useful, unchanged surfaces (-) incipient irregular distortion useless surfaces - strong irregular distortlon Example 4 For the production of dry resist films on a commer-cial scale, the followi.ng procedure was employed:

~242~L0~3 Hoe 82/K 054 A 100 cm wide web of a 25 em thick polyester film which had a rough surface, as indicated in Example 3D and had been precoated with polyvinyl alcohol, was continu-ously coated with a solution of the composition specified in Example 3A, using a slot die. After passing through a drying zone, the resist layer had a -thickness of 38 em and was covered with a polypropylene film. The dry resist film thus produced was stored on a large size roll. By means of a slitter, the large size roll was subsequently cut into handy resist rolls which had a width of 45 cm and a web length of 50 m. By adjusting to an optimum winding tension it was ensured that the roll was, layer by layer, uniformly arranged on the supporting core and did not slip off laterally, i.e., did not telescope.
For comparison, resist rolls were prepared wi-th the same coating solution, however, the polyester film em-ployed had no mat finish and an intermediate layer of polyvinyl alcohol was not provided.
Using a commercial laminator, the films obtained were laminated at 120 C to glass fiber reinforced epoxy laminates, clad with 17.5 em thick copper foils and were then - in the case of the boards having a polyvinyl alcohol intermediate layer, after stripping the support film - exposed in a commercial exposure apparatus (output 5 kWI. The master employed was a line original having line widths and distances down to 60 em.
After exposure, the layers were developed with an 0.8% concentration sodium carbonate solution for 60 sec-onds in a spray processor.

IIoe 82/K 05 The boards were rinsed for 30 seconds with tap water, pre-etched for 30 seconds in a 15% concentration solution of ammonium peroxydisulfate and -then electro-plated for 60 minutes in a copper elec-trolyte bath, Type "GlanzkupferBad", manufactured by Schloetter, Geislingen/
Steige, Federal Republic of Germany.
Current Density : 2.5 A/dm Metal Build-Up : about 30 em.
The following table lists the photosensitivities of the two resist materials, determined with the aid of the wedge steps of the step guide serving as the master and also the widths of the copper paths deposited by electro plating, with respect to three different widths in the master.

TAsLE ON FOLI,OWING PAGE

Hoe 82/K 054 _ Exposure time 1 2 3 4 5 6 7 in seconds _ Wedge Steps Example 4 4.7S.1 5.9 6.0 6.8 7.17.4 Wedge steps reference 3.14.0 4.6 5.0 5.5 6.06.5 sample _ Width of copper path for width 198 190 186 180 178176 174 of 198 em in the master Example 4 Width of copper path 220210 207 198 192 187180 reference sample Width of copper path for width 102 98 94 91 88 85 80 of 102 em in -the master Example 4 _ Wid-th of copper path _110 102 96 92 _ reference sample Width of copper path for width 75 70 68 66 64 _ of 76 em in the master Example 4 Wid-th OfhCOpPer decreasing resistance to developer reference sample --I deterioration of widths of paths --9 Example _ The dry resist film described in Example 4 was lami-nated at 120 C to a 25 x 16 cm glass fiber reinforced epoxy laminate, clad with a 17.5 em thick copper foil.
After storing for 10 minu-tes, the support film was stripped.
The board was irradiated with 150 mW and 1,200 linest2.54 cm (corresponding to 4mJ/cm2) on a commercial laser Hoe 82/K 054 irradiating device (LASERITE 150R, manufactured by Eocom Division of American Hoechst Corporation), equipped with an argon ion laser. In the procedure, the LASERITE
device was coupled with an interposed computer, so that a circuit pattern was produced on the resist layer by way of a non-material master. The non-material image included straight and curved lines at various angular positions, for producing line wid-ths and distances ranging be-tween 200 em and 70 1~m. After irradiation, the board was devel-oped in a 0.8~ concentration sodium carbonate solutionr The resist flanks at the conductive paths had sharp out-lines. The resist stencil was an exact reproduction of the non-material master, independently of the posi-tion and shape of the paths stored.
The baked resist stencil exhibited a very good resis-tance -to electroplating baths so that the board could be provided with faultless and firmly adhering copper paths, for example, in the copper electroplating bath, "Glanzkupfer-Bad", mentioned in Example 4.
Example 6 For producing a positive-working dry resist material, the following coating solutions were prepared:
A. Photosensitive Layer:
34.5 p.b.w. of ethylene glycol monomethyl ether, 21.0 p.b.w. of butanone, 27.5 p.b.w. of a cresol-formaldehyde novolak hav-ing a softening range from 105 to 120 C, determined according to the capil-lary me-thod, DIN 53,181, 5.4 p.b.w. of polyethylene glycol (molecular weight 2000), ~242~L0~
Hoe 82/K 054 9.7 p.b.w. of the polyacetal formed from 2-ethyl-butyraldehyde and triethyl-eneglycol, 0.3 p.b.w. of 2-(4-ethoxy-naphth-1-yl)-4,6-bis-trichloromethyl-s-triazine, 1.9 p.b.w. of a commercial coating auxiliary based on a silicone, and 0.02 p.b.w. o-,- crystal violet base.
B. Intermediate Layer:
200 p.b.w. of a 7% concentration aqueous poly-vinyl alcohol solution, and 1 p.b.w. of polyethylene glycol (molecular weight 2000).
Solution B was used to apply a 1.4 to l em thick polyvinyl alcohol layer to a biaxially stretched and heat-set polyethylene terephthalate film with a rough surface, containing 1.5% by weight of pyrogenic silicon dioxide of an average particle size of 1 em and, on top of this layer, coating solution A was spin-coated in such a way that a layer weight of 45 gJm2 was obtained after drying at 90 to 110 C.
The dry resist film thus produced was laminated to a glass fiber reinforced epoxy laminate clad with a 17.5 em thick copper foil, by means of a commercial laminator, at 110 C. After cooling for ten minutes, the polyester film could be stripped without difficulty. The satin finish surface of the polyvinyl alcohol layer did not change, even after storing for more than 2 hours in a room at 70% rela-tive humidity and 25 C.

~2~0~3 Hoe 82/K 054 The coated board was exposed under a master in the usual manner and developed with a 3.5% concentration tri-sodium phosphate solution. The uncovered copper paths were etched with an iron-III-chloride solution and the resulting circuit pattern had vertical flanks.
It will be obvious to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

Claims

WHAT IS CLAIMED IS:

1. In a photosensitive transfer material comprising a temporary flexible support film and a thermoplastic photosensitive layer thereon, the improvement that the surface of the support film which faces the photosensitive layer is rough.

2. A photosensitive transfer material as claimed in Claim 1, wherein the surface of the photosensitive layer, which faces away from the support film, is covered with a cover film with less adherence to the layer than the support film.

3. A photosensitive transfer material as claimed in Claim 1, wherein the support film is transparent.

4. A photosensitive transfer material as claimed in Claim 1, including, between the photosensitive layer and the support film, a thin intermediate layer which adheres more firmly to the photosensitive layer than to the sup-port film, which does not become tacky upon heating to temperatures up to 150° C, and which is soluble in a developing liquid used for the photosensitive layer.

5. A photosensitive transfer material as claimed in Claim 1, wherein the average surface roughness of the support film is in the range from 0.5 to 5 µm.

6. A photosensitive transfer material as claimed in Claim 4, wherein the intermediate layer has a thickness ranging from 1 to 5 µm.

7. A photosensitive transfer material as claimed in Claim 4, wherein the intermediate layer is water-soluble.

8. A photosensitive transfer material as claimed in Claim 4, wherein the intermediate layer comprises a minor amount of at least one constituent of the photosensitive layer.

9. A photosensitive transfer material as claimed in Claim 1, wherein the photosensitive layer comprises a photopolymerizable layer.

10. A process for manufacturing a photoresist stencil, which comprises laminating a thermoplastic photosensitive layer applied to a flexible support film, with its free surface to a permanent support, exposing the photosensi-tive layer imagewise and developing it into a relief image, after stripping the flexible support film, wherein a transparent support film is used, in which the surface carrying the photosensitive layer is rough and wherein the photosensitive layer is exposed through the support film, before the support film is stripped.

11. A process for manufacturing a photoresist stencil, which comprises using a transfer material composed of a temporary flexible support film, a thin intermediate layer which does not become tacky upon heating to temperatures up to 150° C and a thermoplastic photosensitive layer applied on top of the intermediate layer, the intermediate layer adhering more firmly to the photosensitive layer than to the support film and being soluble in a developing liq-uid used for the photosensitive layer, laminating the transfer material with the free surface of the photosensi-tive layer to a permanent support, stripping the temporary support film, exposing the photosensitive layer imagewise and developing it into a relief image, wherein a temporary support film is used, which has a rough surface, on which the intermediate layer and the photosensitive layer are present.